---
title: "Core Web Vitals Explained — Lemwatch Help"
description: "Understanding LCP, CLS, INP and how to improve them."
canonical: "https://lemwatch.com/help/core-web-vitals"
source: "https://lemwatch.com"
---

# Core Web Vitals Explained

> Understanding LCP, CLS, INP and how to improve them.

## Core Web Vitals Explained

 Google's Core Web Vitals are the three critical metrics that determine user experience and search ranking impact.

### LCP — Largest Contentful Paint

 **What:** How long until the biggest visible element (hero image, heading) loads.

 Rating — Threshold —

 🟢 Good — ≤ 2.5 seconds —

 🟡 Needs work — 2.5–4.0 seconds —

 🔴 Poor — > 4.0 seconds —

 **How to fix:** Optimise images (WebP/AVIF), use a CDN, preload critical resources, reduce server response time.

### CLS — Cumulative Layout Shift

 **What:** How much the page layout shifts unexpectedly while loading.

 Rating — Threshold —

 🟢 Good — ≤ 0.1 —

 🟡 Needs work — 0.1–0.25 —

 🔴 Poor — > 0.25 —

 **How to fix:** Set explicit width/height on images and videos, avoid inserting content above existing content, use CSS aspect-ratio .

### INP — Interaction to Next Paint

 **What:** How quickly the page responds to user interactions (clicks, taps, key presses).

 Rating — Threshold —

 🟢 Good — ≤ 200ms —

 🟡 Needs work — 200–500ms —

 🔴 Poor — > 500ms —

 **How to fix:** Break up long JavaScript tasks, defer non-critical scripts, use web workers for heavy computation.

### How LemWatch Tracks These

 LemWatch runs Lighthouse audits on **both mobile and desktop** viewports. You can compare scores side-by-side on any site's Performance tab, with 7/30/90-day trend charts.

### Why Both Mobile and Desktop Matter

 Google uses mobile-first indexing, so mobile scores directly impact your search ranking. Desktop scores matter for user experience on larger screens. LemWatch tracks both independently.


## Related

- [Help centre](https://lemwatch.com/help)
- [Understanding Your Dashboard](https://lemwatch.com/help/understanding-dashboard)
- [Setting Performance Budgets](https://lemwatch.com/help/performance-budgets)
- [Uptime Monitoring](https://lemwatch.com/help/uptime-monitoring)
- [Lemwatch pricing](https://lemwatch.com/pricing)
- [Creating PDF Reports](https://lemwatch.com/help/creating-pdf-reports)
- [Cookie security check](https://lemwatch.com/help/cookie-security-check)